Earlier today, the Iranian Parliament building in central Tehran was stormed. Attackers, reportedly wearing women’s clothing, shot their way into the complex, and took an unknown number of hostages. Shortly afterwards, two suicide operations hit the shrine of Ayatollah Khomeini to the south of the city.

While the attack was still ongoing, the Islamic State released an official statement on Telegram, claiming that “fighters from the Islamic State are attacking the shrine of Khomeini and the Iranian Parliament building.”

Just under an hour later, the same official channel on Telegram published a short video filmed inside the Parliament building, seemingly shot using a headcam. In it, the attackers could be heard speaking in heavily accented Arabic, declaring that, “We [the Islamic State] will remain until the Final Hour, by the will of Allah.”

It is far too early to predict what will happen in the aftermath of this attack, but its implications could be dire. Here are four likely outcomes: 1. While Iran’s counter-terrorism measures are already sophisticated, an attack like this could provoke a disproportionate response from the government, one that could manifest in increasingly draconian measures against politically active Sunni Muslims. Any disproportionality will reify the Islamic State’s ideological appeal in Iran to no end, especially to those that are already on fence.

2. Iranian officials will be called upon to step up the intervention in Iraq and Syria. Even if there is little more that they can actually do, these calls could result in an intensification in the “war” between Sunni and Shia Islam. This would have the effect of pouring petrol on the Islamic State’s ideological fire.

3. Global Coalition dynamics are complicated enough as it is. Were Iran to intensify its intervention against the Islamic State, this would test it in the extreme, especially given Trump’s new combative stance on Iran.

4. And, perhaps most importantly, the attack will boost the Islamic State’s flagging morale, especially at the footsoldier level. In months to come, it will be used by the group as a way to distract from territorial loss and, beyond that, it will be further weaponised as an ideological bludgeon against the Islamic State’s chief rival, al-Qaeda. Essentially, the group will say: “We, the Islamic State, promised to hit the Safavids. We, the Islamic State, have followed through. Al-Qaeda, on other hand, is friend of Iran, and it has done nothing.” In the global jihadist war of ideas, this will be hugely important.

In sum, this attack against Iran makes strategic sense for the Islamic State in the same way that attacking the United States on 9/11 made strategic sense to Usama bin Ladin.

In the next few days, people will be wondering where this operation came from. Even if the attackers turn out to be foreign nationals, they will have required extensive support from a local network to execute something like this.

Iran is not known for its Islamic State supporters. However, in spite of the fact that it has rarely been spoken about in the media, the group has been agitating there for years now, and its supporters have been around for a long time, with dozens actually travelling to join the group. And, lest we forget, in 2016, the Islamic State eulogised seven Iranians that had died in suicide operations in Iraq and Syria.

Compared to many of its neighbours, Iran has a relatively strong and stable state, and its security services are notoriously effective. That is the principal reason why there has not been an attack there until now. The Islamic State has planned multiple operations in Iran in the past—this is just the first one to be a success.

Whatever happens, its implications could be enormous.

Charlie Winter is a Senior Research Fellow at ICSR. Follow him @charliewinter